Type: C-12 HA 78247A
Spec: 84070-A
Power :110 VAC 1.7 amps
Purpose: Used by broadcast industry, this was a Speech Input Assembly generally used to run two turntables, low impedance microphones (for example: 125 ohms, 450 ohms, 600 ohms) and telephone lines.  All module outputs were for 600 ohm.  At this time, the speech input assembly 12H or C-12H had no limiter as did the later 212A or 212B consoles, but it sometimes fed the Collins 26C Speech Limiter to achieve the 18 to 20db of input gain some of the early broadcasters wanted especially for night time transmission. The 26C limiter had the row of incremental gain step buttons at the bottom . During this era, both were considered to be complementary to each other ( ie the 12H and 26C).  The improved 26W no longer needed them and retained only the two stage rheostat adjustment.

Front of unit. Click on image to enlarge.  (Photo by Doug Hensley W5JV)

Nameplate. (Photo by Doug Hensley W5JV)

A C-12 at KPQ in Washington state.  A young Mark Sorley is at the helm. (Photo courtesy of the  Jerry Lee Lewis photo archive section of the Library of American Broadcasters)

The NBC affiliate WMBG during their 1380 Show. (Photo courtesy of the  Jerry Lee Lewis photo archive section of the Library of American Broadcasters)

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Contributors and Credits:

1) Copy courtesy: J Douglas Hensley <doug.hensley(at)gmail.com>
 

Aug 17/10